The influence of cathode surface microstructure on DC vacuum arcs

Fu, Yuecheng

doi:10.1088/0022-3727/22/1/013

Cited by 22 publications

(7 citation statements)

References 6 publications

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“…It was proposed that the mechanism would be based on the formation emission of metallic vapour jets similar to those observed in low pressure arcs. 20 Considering that this electron emission mechanism is more difficult to operate, it would demand a higher cathode drop, increasing the overall arc voltage. The jets from the weld pool would increase the content of metallic vapours in the arc.…”

Section: Resultsmentioning

confidence: 99%

Low oxidation potential shielding gas instability in GMA welding

Costa¹,

Starling²,

Modenesi³

2009

Science and Technology of Welding and Joining

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Gas metal arc (GMA) welding is one of the most important processes for joining metals. However, this process is characterised by a relatively large number of variables and high sensitivity to changes in operational conditions. Furthermore, GMA welding stability can be degraded by several factors. Although some of these instability problems have been studied extensively a few of them, particularly those linked to the arc transition regions, are still poorly known and studied. The present paper studies a strong process instability characterised by repulsive metal transfer, large variations in welding current and voltage, and the formation of large quantity of spatter. It was observed previously in the welding of low carbon steel with gas shielding of low oxidation potential, and was linked to alterations in electron emission mechanisms on the cathode surface. Welding current and voltage oscillograms, arc light intensity measurements, and high speed filming were used in this study. It was shown that this instability can also occur in the welding of austenitic stainless steels. Indications of its occurrence were also observed in Al. Changes in metal transfer, arc light intensity and welding current and voltage occur simultaneously during the instability. Unstable operation was also characterised by alterations in arc position and shape and by the lack of removal of the oxide layer on the base metal surface. The onset of instability was linked to the occurrence of a rapid short circuit between the electrode and the weld pool.

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Section: Resultsmentioning

confidence: 99%

Low oxidation potential shielding gas instability in GMA welding

Costa¹,

Starling²,

Modenesi³

2009

Science and Technology of Welding and Joining

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“…When the tangent argument in equation ( 7) tends to n / 2 , the resistance in the region r < r l increases ahruptly. From this condition and equation (4) we determine the radius r l where we have used the law of Wiedemann-Franz, and…”

Section: Nu0rq Rl (7)mentioning

confidence: 99%

“…The most complete and reliable U, measurements are those by Reece [l], Grakov [2] and Kesaev [3]. It should, however, be noted that none of these authors paid proper attention to surface cleanness, although it is known to affect the arc voltage U, [4]. Recently [5], the arc voltage and the ionic composition of a cathode plasma were measured at a fixed arc current I = 200 A for a cathode made of 28 elements.…”

Section: Introductionmentioning

confidence: 99%

Arc voltage as a function of cathode thermophysical properties

Nemirovskii

Puchkarev

1992

J. Phys. D: Appl. Phys.

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Using a model of the continuous metal-to-plasma transition, a simple formula relating the arc voltage to the cathode thermophysical properties, such as the Lorentz constant, heat capacity and energy deposition into arc, has been derived. A formula for the erosion rate has also been derived. The ratio of arc voltage to erosion rate has been used to compare theoretical and experimental data. In view of this analysis, a higher erosion rate than that obtained experimentally is predicted.

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“…The heat modifies the surface by forming a so-called converted layer of few microns [7][8][9]. Several research papers have discussed the association and dynamics of the cathode spot with surface roughness [10,11], surface contamination [12,13], surface temperature [14], inclusions [15], steering magnetic field [16], and material properties like work function [17] and cohesive energy [18][19][20]. The significance of material properties of the cathode, e.g., work function and cohesive energy become prominent in the dynamics of the cathode spot, especially if the cathode comprises more than one phase.…”

Section: Introductionmentioning

confidence: 99%

Effect of work function and cohesive energy of the constituent phases of Ti-50 at.% Al cathode during arc deposition of Ti-Al-N coatings

Syed

Jöesaar

Polcik

et al. 2019

Surface and Coatings Technology

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The differences in work function (W.F.) and cohesive energy (C.E.) of the phases constituting the cathode, plays an important role in the formation of the converted layer at its nearsurface region during cathodic arc deposition. As a consequence, this also affects the deposition conditions for the coatings. In this study, we explore the effect of W.F. and C.E. of the constituent phases during arc evaporation by utilizing two kinds of customized Ti-50 at.% Al cathodes with different phase compositions. Our results show that during reactive arc evaporation the disparity in W.F. and C.E. among the constituent phases of Ti-50 at.% Al cathodes leads to preferential erosion of the phases with lower W.F. and C.E.. The aforementioned preferential erosion begets higher surface roughness on the Ti-50 at.% Al cathode with a wider range of W.F. and C.E. disparity. It is also observed that the thermal conductivity of the Ti-50 at.% Al cathode plays a dominant role in the deposition rate of Ti-Al-N coating. This article also presents how the surface geometry of the cathode in the presence of arc guiding magnetic field significantly influences the microstructure of the deposited coatings.

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The influence of cathode surface microstructure on DC vacuum arcs

Cited by 22 publications

References 6 publications

Low oxidation potential shielding gas instability in GMA welding

Low oxidation potential shielding gas instability in GMA welding

Arc voltage as a function of cathode thermophysical properties

Effect of work function and cohesive energy of the constituent phases of Ti-50 at.% Al cathode during arc deposition of Ti-Al-N coatings

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The influence of cathode surface microstructure on DC vacuum arcs

Cited by 22 publications

References 6 publications

Low oxidation potential shielding gas instability in GMA welding

Low oxidation potential shielding gas instability in GMA welding

Arc voltage as a function of cathode thermophysical properties

Effect of work function and cohesive energy of the constituent phases of Ti-50 at.% Al cathode during arc deposition of Ti-Al-N coatings

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Product

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About

Effect of work function and cohesive energy of the constituent phases of Ti-50 at.% Al cathode during arc deposition of Ti-Al-N coatings